This invention pertains to gas shielded metal arc welding apparatus of the type using consumable wire electrode material to provide filler metal in an arc welding process requiring a supply of shielding gas and means for cooling of the torch head. More particularly, the invention relates to an improvement in such apparatus for welding internal walls in a workpiece having limited access to the joint to be welded.
Shielded gas metal arc welding apparatus of the type described above is conventional and well-known, and in commercial form usually comprises a hand-held insulated torch body with a closely attached torch head and means for feeding consumable wire electrode, electric power, and shielding gas through the handle of the torch body to the torch head. Such a welding process is abbreviated herein as a GMA process, which may optionally employ means to supply cooling water to and from the torch head. While conventional GMA apparatus is suitable for external welding, where the size of the torch does not matter, it is unsuitable for welding internal walls in the workpiece where limited access is provided to the welding area. A typical problem is the need to weld the internal blades of compressor impellers to an adjacent disk, and/or counter disk, where the only access to the weld joint is through the compressor discharge opening, usually having between 8 and 30 millimeter spacing between disks. An additional problem in welding compressor impellers is that the blade constantly changes shape and direction between the interior and exterior of the impeller, leaving a "blind" weld to be carried out.
One solution to this problem is disclosed in my U.S. Pat. No. 4,133,469 issued Jan. 9, 1979, which suggests a GMA welding apparatus using a flexible probe-type torch head which tracks the weld joint by means of a guide tube. An elongated U-shaped guide tube is bent to conform to the weld joint configuration with the "U" facing toward the joint between internal walls to be welded. A torch head attached to a flexible braided copper conductor sheath carrying electric power and enclosing plastic water cooling lines, an electrode wire guide tube and a gas tube. The torch head is inserted into the guide tube by the flexible sheath, and the torch head is pulled toward the discharge opening of the impeller by the flexible sheath. The guide tube maintains distance and attitude of the torch head with respect to the weld joint. One of the problems with the foregoing method is that guide tubes for every design welded must be made and kept on hand.
The present invention is an improvement in a limited access GMA welding apparatus which does not require guide tubes and is adaptable to various weld joint configurations.
Accordingly, one object of the present invention is to provide an improvement in GMA welding apparatus which is adapted to welding internal walls in a workpiece having limited access to the joint to be welded.
Another object of the invention is to provide a limited access GMA torch providing improved weld quality and reducing welding costs in the manufacture of compressor impellers.